An identification system exists whereby a single microprocessor can simultaneously receive sensory input with its subcarrier removed and demodulate the data content on each sensory input. In turn, each sensory input can come from any number of different subcarriers. Such subcarriers include a 40 kHz infrared on/off shift key, and a 447.5 kHz infrared on/off shift key.
The ability to be somewhat media independent has assisted in solving different problems in locating technologies. Such problems include the changing from a low frequency IR carrier to a high frequency IR carrier. The use of higher frequency IR carriers (i.e. 447.5 kHz receivers) are much less likely to obtain optical interference signals caused by the use of newer kinds of fluorescent lighting.
Further use of other subcarriers used with this type of system is a frequency shift keyed (FSK) receiver with appropriate transmitters whose sole combined purpose is to transmit a 10 bit identification code when the transmitter's button is pushed, indicating a special event the user wishes to create. The sensor in this case has a microprocessor that completely demodulates the FSK received code and retransmits that code to a distant microprocessor in such a way that it looks like a demodulated signal from an IR sensor.
U.S. Pat. No. 5,301,353 to Borras et al. discloses a communication system and apparatus wherein the system utilizes one of two different types of communication methods, depending on the location of the user. When the user is in an on-site area, the user communicates via infrared techniques. When the user is in an off-site area, the user communicates using a different communication media, including an RF communication media.
U.S. Pat. No. 5,218,344 to Ricketts discloses a method and system for monitoring personnel in a facility, wherein the system utilizes two different types of communication devices. The system includes a central computer, a plurality of remotely located stationary transceivers, and a portable transceiver unit worn by each monitored individual. In operation, the main computer transmits command signals to a plurality of stationary transceivers using hardwire communication of acoustic, electromagnetic or optical communications. The stationary transceivers then broadcast interrogation signals to the portable transceiver units. The interrogation signals are transmitted via acoustic, electromagnetic or optical transmission methods. The method and system provides a verification of the location of individuals wearing the portable transceiver units.
U.S. Pat. No. 5,228,449 to Christ et al. discloses a system and method for detecting out-of-hospital cardiac emergencies and summoning emergency assistance. The system includes an infrared patient detecting system and an RF communication system. In operation, the infrared system is used to detect the presence and health of the patient. The infrared system provides information to the RF transmitter, which transmits the information to a central computer. The operator of the central computer is then able to monitor the health and presence of the patient via the infrared and radio frequency communication links.
U.S. Pat. Nos. 4,924,211 to Davies and 5,416,468 to Baumann disclose systems and methods for monitoring personnel, wherein the systems comprise both infrared and radio frequency communication devices.
U.S. Pat. Nos. 4,462,022; 4,982,176; 5,570,079; 5,283,549; and 5,578,989 show security systems using local infrared detecting devices which communicate with a central monitoring station via a radio frequency communication link.
U.S. Pat. No. 5,027,314 discloses a system and method for tracking a number of subjects in a plurality of areas. The system includes a plurality of transmitters associated with the subjects, a plurality of receivers associated with the areas and a centralized processor for determining in which of the areas the transmitter and, consequently, the subjects are located.
Each transmitter transmits a light-based signal, such as an infrared signal, representative of an identifying code unique to the transmitter. Each receiver validates the signal to determine whether the signals are representative of the unique identifying codes associated with the transmitters. The centralized processor records the validated signals and receivers, scans the receivers and accumulates areas and badge counts for each area.
U.S. Pat. No. 5,548,637 discloses an automated method and system for providing the location of a person or object (i.e. a subject) in the form of a message in response to a telephone caller's inquiry. The method and system may connect the caller directly to the telephone extension located nearest the subject of interest. A transmitter, such as an infrared transmitter, is attached to each subject to be monitored within a defined area such as a building. A number of receivers or sensors track the location of the subject within the building. The locations are stored in a database. In one form of the invention, as each transmitter is transported throughout the building, the system continually updates the transmitter location in the database.
U.S. Pat. No. 5,572,195 discloses a method and system for tracking an locating objects wherein the system includes a computer network, such as a local area network, a computer connected to the computer network, infrared sensors, and interface circuitry connecting the computer network to the infrared sensors. The infrared sensors are adapted to receive unique identifying codes from infrared transmitters and then provide the codes to the interface circuitry. In turn, the codes are then provided to the computer network. The invention may be implemented using an object identifier variable-based protocol such as SNMP (Simple Network Management Protocol). The system may include an external device controller, such as a relay controller, for controlling a physical device such as an electronic door lock within the environment.
U.S. Pat. No. 5,387,993 discloses various methods of transmitting data and control information such as battery life for badges (TAGs) to optical (i.e. infrared) receivers of an optical locator system. In one of the methods, the badges are "motion-detectabl" and have a sleep mode. The badges are reprogrammable with identifying information about the objects to which they are attached. Each badge activates the sleep mode, thereby reducing its normal power consumption. Each TAG will reactivate the sleep mode when motion is detected by the motion detector, thereby returning the battery power level to normal.
U.S. Pat. No. 5,119,104 discloses a radio-location system for multipath environments, such as for tracking objects in a facility, includes an array of receivers distributed within the tracking area, coupled to a system processor over a LAN. A TAG transmitter located with each object transmits, at selected intervals, spread spectrum TAG transmissions including at least a unique TAG ID. Object location is accomplished by time-of-arrival (TOA) differentiation, with each receiver including a TOA trigger circuit for triggering on arrival of a TAG transmission, and a time base latching circuit for latching the TOA count from an 800 MHz time base counter. In a low resolution embodiment, each receiver of the array is assigned a specific location-area, and receives TAG transmissions almost exclusively from TAGs located in that area, thereby eliminating the need for any time-of-arrival circuitry.
U.S. Pat. No. 5,276,496 discloses an optical receiver for use with an optical location system that locates a target in a defined area. A spherical lens is placed over the area. The area is divided into sections, with a sensor associated with each section. These sensors receive light transmitted through the lens, and are positioned relative to each other and with respect to the lens, such that each sensor receives emitted light from the same size section if the target is located in its section. The height of each sensor may be adjusted so that each sensor receives light of the same intensity if the target is located in its section.
U.S. Pat. No. 5,355,222 discloses an optical location system for locating the position of a moving object in a defined area. An optical transmitter is attached to the moving object. A stationary receiver has a number of sensors for receiving a signal from the transmitter. one sensor has a field of view of the entire area. other sensors have partially blocked fields of view, with the blocking being accomplished with nonopaque strips of decreasing width. These strips are arranged so that the detection or nondetection of light by the sensors can be digitally coded in a manner that corresponds to sections of the area.
U.S. Pat. No. 4,906,853 discloses a control apparatus f or triggering a periodic pulse at random times comprising a timer for variably issuing the periodic pulse in a defined time cycle and a signal generator for variably generating an output voltage within the defined cycle. The signal generator has a light sensitive component for varying in time the generation of the output voltage in proportion to the intensity of visible light incident on the light sensitive component. The apparatus also includes a circuit for applying the generated output voltage to the timer for triggering the issuance of the periodic pulses.
U.S. Pat. No. 5,017,794 discloses apparatus including a time for generating a periodic pulse in a defined time cycle in response to a control signal, and a signal generator for variably generating the control signal within the defined cycle. The signal generator includes a light sensitive component for varying in time the generation of the control signal in proportion to the light incident on the light sensitive component for a portion of the defined cycle.